def triangle_area(x1, y1, x2, y2, x3, y3):
    return abs((x1 * (y2 - y3) + x2 * (y3 - y1) + x3 * (y1 - y2)) / 2.0)

x1,y1,x2,y2,x3,y3 = map(int,input().split())
cases = ((0,1),(0,-1),(-1,0),(1,0))

ans = 0
for i in range(4):
    p1,q1 = x1 + cases[i][0], y1 + cases[i][1]
    for j in range(4):
        p2,q2 = x2 + cases[j][0], y2 + cases[j][1]
        for k in range(4):
            p3,q3 = x3 + cases[k][0], y3 + cases[k][1]
            area = triangle_area(p1, q1, p2, q2, p3, q3)
            ans = max(ans, area)
            
print(ans)